This invention relates generally to an electrostatographic printing machine, and more particularly concerns a sheet of support material utilized in the sheet feeding apparatus thereof.
In the process of electrostatographic printing, an electrostatic latent image is created which corresponds to the original document. The electrostatic latent image is reproduced in viewable form on a sheet of support material. Electrostatographic printing includes electrophotographic printing and electrographic printing. In the process of electrophotographic printing, as disclosed in U.S. Pat. No. 2,297,691 issued to Carlson in 1942, a photoconductive layer is charged to a substantially uniform potential in order to sensitize its surface. A light image of the original document is projected onto the charged photoconductive surface. The charge on the photoconductive surface is selectively dissipated in the irradiated areas to record thereon an electrostatic latent image of the original document. A developer mix comprising heat settable dyed, colored thermoplastic powder, known in the art as toner particles, and coarser carrier granules, such as ferromagnetic granules, is brought into contact with the electrostatic latent image. The toner particles are attracted electrostatically from the carrier granules to the latent image recorded on the photoconductive layer. Thereafter, the toner powder image developed on the photoconductive layer is transferred to a sheet of support material. The toner powder image is then permanently affixed to the support material. Electrographic printing differs from electrophotographic printing primarily in that an insulating medium is utilized to form, without the aid of a light image, the electrostatic latent image. Other than that, electrographic printing and electrophotographic printing are substantially identical to one another.
Multi-color electrophotographic printing is substantially the same as the heretofore discussed process for black and white printing. However, a plurality of single color toner powder images are formed and thereupon transferred to the sheet of support material in superimposed registration with one another to create a multi-color copy corresponding in color to the original document. The multicolor electrophotographic machine is generally provided with cut sheets of support material. The sheets are used as image receiving members in the printing machine. Although paper is the most commonly used sheet material, certain non-fibrous sheets characterized generally by having a high surface gloss and a smooth surface are increasingly utilized. These non-fibrous sheets are frequently more durable than paper and, when transparent, have great utility as transparencies, i. e. a conventional projector may project images therefrom onto a screen.
Generally, the sheet of support material is of a pre-selected size and advances through the printing machine, one sheet at a time, for suitable processing therein. Inasmuch as copies may be made at high speeds, it is advantageous to stack a pile of sheets in the printing machine feeding mechanism which automatically advances one sheet at a time therefrom. Sheets are continuously advanced from the stack until the stack is depleted, whereupon the operator refills the machine with a new stack of sheets. However, when non-fibrous sheet material is substituted for paper, operational difficulties frequently occur. For example, in feeding successive non-fibrous sheets, it has been found that the uppermost sheet often causes creep or advancement of the sheets immediately therebelow. This results in misfeeds and jams within the printing machine, thereby greatly increasing the amount of wasted sheets and the ensuing cost of the operation. In addition, machine downtime, i. e. the time necessary to clear the machine of sheet jams, is substantially increased when misfeeds or jams occur. It appears that jams or misfeeds are primarily caused by the relatively high sliding friction between successive non-fibrous sheets.
As hereinbefore mentioned, the utilization of non-fibrous sheets for the formation of multi-color transparencies is highly significant with the advent of multi-color printing. In multi-color electrophotographic printing machines, it is highly desirable to have the capability of creating multi-color transparencies. Hence, there is a continuing need for trouble-free feeding and processing of the non-fibrous sheet material.
Accordingly, it is a primary object of the present invention to improve the transparency support material so that successive sheet feeding thereof is readily achieved.